I did buy the Solar Force 15watt solar panel at west marine for about 70 bucks. and another 25 for the controller.
I have not installed either yet, will keep you updated.
BUT.... after spending 2 nights on the boat, and off the shore power for 2 weeks now - both batteries are still 'full'. maybe the 15watt is overkill, but cost/watt is better than the 5 watt trickle charge.